Canon LBP3300 Series, Service Manual

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Chapter 2
2-9
When the last step in this block is complete, a negative electrical charge is remained in the unexposed drum surface area by the laser beam and it is removed from
the exposed area.
The image with a negative charge on the drum is called an "electrostatic latent image" as it is invisible to the human eyes.
F-2-9
Step 1: Primary charging
F-2-10
As a preparation to form a latent image, the surface of the photosensitive drum is charged a uniform negative potential in this step. The charging method of this
printer is to charge directly to the drum surface.
The primary charging roller is made of a conductive rubber. To maintain the surface potential charged on the photosensitive drum uniformly, the DC bias and ad-
ditional AC bias are combined.
This DC bias, interlocked to the developing DC bias, changes according to the IMAGE DENSITY INFORMATION signal from the video controller.
Step 2: Laser beam exposure
As the laser beam scans the photosensitive drum, the potential on the exposed area gets neutralized and this area forms the electrostatic latent image.
F-2-11
2.4.1.4 Development block
0011-2455
The electrostatic latent image on the photosensitive drum surface is visualized by applying the toner in this process. This printer utilizes the projection development
method by the single-component toner.
Step 3: Development
0
-100
-500
Time (t)
Surface electric potential (V)
Exposed area
Laser
beam
exposure
(step 2)
Transfer
(step 4)
Primary
charging
(step 1)
Primary
charging
(step 1)
Unexposed area
Photosensitive drum
Primary charging roller
AC bias
DC bias
Laser beam
Unexposed area Exposed area